<?php

abstract class Usb
{
    public function start()
    {
        echo "<h3>usb start</h3>";
    }

    public function run()
    {
        echo "<h3>usb start</h3>";
    }

    abstract public function stop();
}

class Upan extends Usb
{
    public function stop()
    {
        echo "<h3>usb stop</h3>";
    }

    public function explode()
    {
        echo "<h3>usb explode</h3>";
    }
}

$u1 = new Upan();
$u1->start();
$u1->run();
$u1->stop();
$u1->explode();
